1. Field of the Invention
This invention relates to an electro-optical device in an image display adapted to drive an electro-optic material layer which uses plasma to select pixels.
2. Description of the Related Art
As the means for providing, for example, a liquid crystal display with high resolution and high contrast, there is generally provided active elements, such as transistors, etc. to drive every display pixel (which is referred to as an active matrix addressing system).
In this case, however, since it is necessary to provide a large number of semiconductor elements such as thin film transistors, the problem of yield results particularly when the display area is enlarged, giving rise to the great problem that the cost is necessarily increased.
Thus, as the means for solving this, Buzak et al. have proposed in the Japanese Laid Open Application No. 217396/89 publication a method utilizing discharge plasma in place of semiconductor elements such as MOS transistors or thin film transistors, etc. as an active element.
The configuration of an image display device for driving a liquid crystal by making use of discharge plasma will be briefly described below.
This image display device is called a Plasma Addressed Liquid Crystal display device (PALC). As shown in FIG. 6 of the present drawings, a liquid crystal layer 101 serving as an electro-optic material layer and plasma chambers 102 are adjacently arranged on an opposite side of a thin dielectric sheet 103 comprised of glass, etc.
The plasma chambers 102 are constituted by forming a plurality of grooves 105 in parallel to each other in a glass substrate or base plate 104. These chambers are filled with an ionizable gas. Further, pairs of electrodes 106 and 107 are provided in the grooves 105 in parallel to each other. These electrodes 106 and 107 function as an anode and a cathode for ionizing the gas within the plasma chambers 102 to generate a discharge plasma.
The liquid crystal portion of the display has the liquid crystal layer 101 held between the dielectric sheet 103 and a transparent base plate 108. On the surface of the transparent base plate 108 at the liquid crystal layer 101 side are formed transparent electrodes 109. These transparent electrodes 109 are perpendicular to the plasma chambers 102 constituted by the grooves 105. The locations where the transparent electrodes 109 and the plasma chambers 102 intersect with each other correspond to respective pixels.
In the above-mentioned image display device, by switching and scanning the plasma chambers 102 in sequence where a plasma discharge is to be carried out, and applying signal voltages to the transparent electrodes 109 on the liquid crystal layer 101 side in synchronism with the switching scan operation, these signal voltages are held by respective pixels. The liquid crystal layer 101 is thus driven.
Accordingly, the grooves 105, i.e., plasma chambers 102 respectively correspond to one scanning line, and the discharge region is divided every scanning unit.
In image display devices utilizing discharge plasma as described above, an enlarged display area is more easily realized than larger areas utilizing semiconductor elements, but various problems arise in putting such a device into practice.
For example, forming the grooves 105 which constitute the plasma chambers 102 on the transparent glass substrate 104 raises considerable manufacturing problems. In particular, it is extremely difficult to form such grooves at a high density.
Further, it is required to form the electrodes 106 and 107 which generate the discharge in the grooves 105. However, an etching process which form the electrodes is troublesome, and it is difficult to maintain the spacing between electrodes 106 and 107 accurately.